I can confirm that Monal 1.04 works fine in OS4. While it doesn't fall under the class of programs allowed to multi task, I am planning on adding fast switch and task completion which should hopefully allow you to switch between programs quickly without losing your connection.
Work on Monal 1.05 will resume this week. Before OS4 comes out I want to get another version out that is focused on bug fixes and server compatibility. If you are aware of public servers that do not work, let me know in the comments section. If it is a private server and you can give me access to test, contact me at anurodhp@SPAM.gmail.com (remove the spam) with instructions. I will make sure it works in the next release.