To solve your concern that HttpURLConnection may be hang, I think that we can set the timeout values (for example, 1 second) with functions setConnectTimeout() and setReadTimeout(). I uploaded a new patch that incorporated this solution.
In my opinion, unless we do not show the links to the documents, we should show "alive" links because it gives the user the feeling that we still care about Tajo (i.e., this produce has not been abandoned yet). Hence, I think that showing alive links to either a specific version or the current version is important. However, although showing an "available" version is important, showing "the latest" version is less important. When an old version of Tajo is installed, we should show the documents of that old version if they are available.
If you change the workflow to use pull requests for submitting patches, please update Tajo's web page "How to Contribute to Tajo" with new instructions.