If you contribute code that you have written yourself, then it must be contributed under the same license as the PortletMVC4Spring project, specifically the Apache License, Version 2.0.
If you contribute code that you have not written yourself (i.e. copied from elsewhere), then the original license that governs the contribution must be kept in place. The original license must be clearly referenced in the contribution and must be compatible with the Apache License, Version 2.0.
Contributions must be received in the form of GitHub pull requests and must adhere to the requirements of the DCO by adding a "Signed-off-by" line to commit messages.
For example:
Implement feature X.
Signed-off-by: Developer Name <developer@mycompany.com>
Note that Git as has a convenient -s command line option that will automatically append the "Signed-off-by" line to
a commit message:
$ git commit -s -m 'Implement feature X.'
Pull requests that do not contain the "Signed-off-by" line in commit messages will have their status automatically
set to failed by the GitHub DCO Enforcement Application.