Section 4, Definition 4 Covered Entity, emphasis added:

The term "covered entity" means a device manufacturer, a software manufacturer, an electronic communication service, a remote computing service, a provider of wire or electronic communication service, a provider of a remote computing service, or any person who provides a product or method to facilitate a communication or the processing or storage of data.

This definition seems extremely broad, and could be stretched to cover an answerer on Stack Overflow whose answer provided a method facilitating data processing, storage, or communication (which covers most software methods). So let's then look at what can be required of a covered entity:

Section 3(a)(1), Requirement:

... a covered entity that receives a court order from a government for information or data shall provide such information or data to such government in an intelligible format or provide technical assistance as is necessary to obtain such information or data in an intelligible format or to achieve the purpose of the court order.

Subsection 2 limits the scope so that a covered entity only has to provide data if the data was "made unintelligible by a feature, product, or service owned, controlled, created, or provided by the covered entity or by a third party on behalf of the covered entity."

However, courts cannot effectively require people to do the impossible; if a programmer wrote a method that was used in an encrypted communication service that does not mean the programmer, lacking the encryption key, will be forced to break what they believe to be unbreakable encryption.

The key here is in section 3(c), emphasis added:

A provider of remote computing service or electronic communication service to the public that distributes licenses for products, services, applications, or software of or by a covered entity shall ensure that any such products, services, applications, or software distributed by such person be capable of complying with subsection (a).

So if this bill were to become law, it would be the service provider who's responsible for making sure the government can get the intelligible information. The government could require e.g. the author of the encryption function, even if that person's not part of the service provider, to help break the encryption, but the responsibility for ensuring data accessibility lies with the service provider.

The definition of service provider seems absent from at least what I can see of this bill, but it seems that a company selling a communications service to customers would very likely qualify, and a person/company who posted an answer on SO that was then picked up and integrated into something someone else distributed as part of a service, very likely would not.