Thank you for your interest in contributing to the openEHR ecosystem!
openEHR SDK is release open source under the Apache 2.0 license, but many of the people working on it do so as their day job. The goal is to establish some semi-formal development processes and hopefully make those efforts and communication go more smoothly. Enhancement proposals are very welcome at this stage as well.
All contributions are welcome at all times. There is no need to be a developer to actively contribute, and your first contribution is taking interest in the openEHR SDK and openEHR and / or by using it.
For general questions the probably best place to ask is the official openEHR discourse.
For more technical questions, enhancements or problems with the SDK itself, open an according issue and fill in the template, so that adequate steps can be taken to resolve your issue.
If you wish to contribute code, there are a few more things to consider.
If you want to implement a bigger enhancement, addition or change to the SDK, consider opening an enhancement issue first, proposing and explaining your intended change, giving other contributors the option to discuss the need and impact of the idea.
Otherwise, assuming regular code and software development best practices and the coding conventions, simply open a pull request, and also fill in the template and describe your change. One of the core contributors will review the change as soon as possible.
Please be respectful in giving and receiving feedback and potentially criticism, and keep the code of conduct in mind.
When your change has been merged, you've successfully contributed to openEHR SDK development!