When your last smartphone started to get a little long in the tooth, you probably just bought a new one. Maybe you kept the old one around as a backup. Maybe you recycled it. But, chances are, whatever you did, you didn't physically upgrade the thing. You didn't toss in more memory or a new processor or any aftermarket parts.

In the desktop computing era, upgrading your machine was common practice. Amateur users could replace motherboards, processors, memory, hard drives, video cards, and other components with relative ease. But the prevalence of ever smaller laptops, and now smartphones, means that user upgrades are quickly becoming a thing of the past.

Part of this phenomenon is due to the design of the new devices. Their smaller form factors make them harder to take apart and access the components, and many of these devices arrive from the factory fully sealed, so you can't tinker with them without highly specialized tools. Another key factor is cost: it's often cheaper to buy a whole new device than to swap out components. And let's not overlook how difficult it's becoming to get your hands on the extra hardware. There aren't many companies selling component upgrades for smartphones.

>'We believe in choice, and we want to make mobile computing as free as we're used to it in the PC world' Sebastian Krzyszkowiak

But a German company called Golden Delicious, together with an open source community called OpenPhoenux, is trying to change all that. Golden Delicious will soon offer a tiny motherboard that lets you upgrade a Nokia N900 – an iconic phone with a full-hardware keyboard, part of a dying breed in the world of mobile devices – and the team hopes to provide a thriving hardware and software ecosystem around this and other phones.

"We believe in choice, and we want to make mobile computing as free as we're used to it in the PC world," says Sebastian Krzyszkowiak, one of the project's core developers.

The project is called the Neo900, and the replacement board is based on the GTA04 platform from Golden Delicious. Those who don't want to get their hands dirty – or don't have an N900 lying around – will be able to purchase fully assembled Neo900 phones, based on existing N900 cases.

The new board will cost between 500 and 700 Euro and will include a high speed LTE wireless modem, a faster processor, more RAM, support for battery hot swapping and several new sensors, including a gyroscope and compass. Just like the N900, the phones will run Maemo, a Linux-based, open-source mobile operating system formerly developed by Nokia.

It may sound like an odd project, but it has already raised 25,000 Euro through a web-based crowdfunding campaign. Nokia dropped the N900 when it got into bed with Microsoft and its Windows Mobile operating system in 2010, but the phone still has a strong cult following. And similar projects built around other phones have had some success as well. Golden Delicious already sells GTA04-based hardware upgrades for a line of Linux smartphones called the Neo 1973 and the Neo FreeRunner.

Krzyszkowiak says the N900 was the obvious choice. The project needed to tap into a large number of committed users, and there's still a vibrant community behind the N900 and Maemo. Although Nokia has ceased development on Maemo, there's an active group of people contributing code to the project.

"N900 was one of the most open smartphones ever released by any big tech company," he says. "While Maemo wasn't even near being 100% free, the N900 can be operated with almost fully open stack - the only thing missing is the bootloader."

The N900's full keyboard also helps differentiate the project from all the touch-screen-only smartphones on the market, Krzyszkowiak says. The decision to stick with the N900's resistive touch screen – instead of upgrading to a capacitive screen – is one of the most controversial aspects of the project, but Krzyszkowiak says they wouldn't change it even if they could.

"The screen from the N900 is...exceptionally sensitive and allows us to get accuracy that's not reachable by any capacitive screen, enabling power users to launch software that's not optimized for touchscreen usage or even use their phones as an artistic canvas," he says.

>'We do not want to build an Überphone to compete against iOS and Android. We want to support the open source community like an indie label' Nikolaus Schaller

While there's plenty of enthusiasm for the project – and a surprising amount of money pledged up-front – there are still a few challenges. One is the increasingly litigious tech industry. But when the patent question comes up, Nikolaus Schaller of Golden Delicious, says that what they're doing is similar to putting together a PC with an assortment of existing hardware. In other words, any concern about patent violations would fall on the actual manufacturers of the components, not on Golden Delicious.

Finding N900 cases may be a challenge, but the team is confident they can make things work. If they can't find enough, Krzyszkowiak says, they will start to refurbish complete N990s. Yes, there are only so many phones out there. But unlike Canonical or Mozilla – both of which are aiming for mass-market adoption of their respective open-source mobile operating systems – the Neo900 team is happy to be working on a niche project.

"We do not want to build an Überphone to compete against iOS and Android," Schaller says. "We want to support the open source community like an indie label...We want to serve the needs of 'our' customers, not the needs of some intermediates like mobile network operators looking for some new ideas or means to advertise their network contracts."

Because the project uses open hardware, other operating systems could also run on the Neo900, including Ubuntu Touch, Firefox OS, SHR, or free Android variants like Replicant. "We hope that Neo900 will cause a new blood to appear in all those projects, and things will keep going faster and faster," Krzyszkowiak says.

He believes the project is particularly important now that the press has revealed the NSA's efforts to track our behavior via online technology, most notably technology run by the giants of the industry, including Google. "We're also committed to make our devices as free as possible and ensure that there are no hidden backdoors – especially after the latest surveillance reports"

It's not just about upgrading your phone. It's about having complete control.