First of all, Jackhammer is not abandoned. Moreover, I began testing it as a mapper, not only a coder. A 64-bit version of the editor is being developed, that would eliminate some critial problems with memory allocations (e.g. when undo grows too large). Win64 users will be able to select which Jackhammer build to install, while Win32 users are still limited to 32-bit build. We've also updated to the recent Qt 4.8.6. 64-bit Linux build is also planned. Please be patient, everything is going okay. :)
Second, but not less important. If you are not willing to donate funds (I can't judge you, since most of HL1/Quake1/2/3 mappers are non-profit developers), you can at least support my latest HL1 mod on Greenlight - "Headcrab Frenzy" (ModDB Profile). Note that its levels were edited in Jackhammer. I will also appreciate if you spread the word about this mod amongst other HL1 fans.