If it is open source, then at least you can recompile and/or port to a new OS.

The OP says, "I can't code in any meaningful way, nor do I aspire to"

You have the option of paying someone to fix a problem.

The OP says, "I could easily pay for a supported version of icewm, but I can't personally pay someone enough to keep it alive."

You have none of those options if the closed-source producer of a package arbitrarily decides to drop it.

What you've written is true, there are more options for open source projects. However, exercising those options just may not be feasible, as the OP points out in this particular case. If resources for continued development cannot be found, the open source project is effectively just as dead.