Development has been slow lately, but Quicksilver[0] is still around as a FOSS alternative. We have an upcoming release that should refresh things a bit for Seqouia.
Launchbar[0] is also still around - not actively developed, but actively maintained. Happy user since 10 years already, even though I own a lifetime Alfred license.
[0]: https://github.com/quicksilver/Quicksilver