A random suggestion, then: perhaps try selling it for a few months, and if the number of sales starts to tail off and you still feel uncompensated, set a fundraising goal at which you'd release it open source?
As others said, I'm more interested in donating (and helping to persuade others to) to make it available for everyone than I am in buying a copy.
I certainly appreciate that. But also, open source and business models are not mutually exclusive. Perhaps you can open source the core code and then charge for support or extensions, like many others do with Linux, Apache, etc.
Plus, if you have more people contributing changes/additions, you might have less of a workload.
One last question for you: if I pay, do I get the source that I can tinker with/extend, or is it in a minified/obfuscated format?
As others said, I'm more interested in donating (and helping to persuade others to) to make it available for everyone than I am in buying a copy.
http://www.indiegogo.com/projects/tern-intelligent-javascrip... is an example of successfully raising money for a javascript tool, although in that case the money was raised before the work was finished.