Microsoft must work with, not against, open source otherwise it risks sacrificing developer support and credibility among customers - even Windows loyalists.

That's according to the chief executive of a fast growing open source competitor to Microsoft's popular, but closed-source, SQL Server database.

Marten Mickos, MySQL chief executive, told The Register the secret to growth in Microsoft's core Windows franchise lies in working with open source.

According to Mickos: "If you won't work with MySQL, PHP and Ruby then you are lost - that's always been our message."

Microsoft is clearly aware it must ensure open source languages, middleware and applications run just as well on Windows as Windows-only languages, middleware and applications, otherwise open source developers will deploy on Linux.

As such, Microsoft has technology deals with SugarCRM, Zend Technologies, JBoss (now part of Red Hat) and Novell, while it's devised versions of Python and Ruby for the .NET Framework. MySQL, meanwhile, last year joined Microsoft's Visual Studio Industry Partner (VSIP) program and developed a Visual Studio plug in for developers building applications for its database.

There's plenty of scope left to help developers using Visual Studio for MySQL and to improve data, analytics and application interoperability between MySQL, SQL Server and other Microsoft server and Office applications.

Speaking in the wake of claims in Fortune by Microsoft's legal team that Linux and open source infringe on 235 of the company's patents, Mickos suggested, though, that Microsoft isn't going far enough in its efforts with open source, and that this will cost the company dearly.

"I don't think you can say Microsoft is pragmatic on open source - it's religious. It's categorical in a way it shouldn't be, and it's harming them," Mickos said.

"You must never lose the trust of the customer [even] customers who are not using open source. They are looking at Microsoft and asking: 'why are you doing that?' People have a sense of fairness, and you don't want to get hurt.

"It hurts their credibility with customers. The question that arises is if Microsoft is ready to sue Linux for patent infringement, what says they won't sue a customer? As an end user, I'd be worried if I was using a vendor that threatens to sue me."

MySQL is certainly leveraging the Microsoft fear factor. With 700 partners in the systems integrator, VAR and ISV markets, Mickos's company is promising that - unlike Microsoft - it won't end up competing with them, should they develop a lucrative business. Some 60 per cent of MySQL revenue comes form the embedded market, with partners OEMing MySQL's database.

"We are sticking to the knitting - the database," Mickos promised. ®