Hacker TheFlow released Adrenaline v3 for PS vita a couple days ago.
The popular ePSP CFW brought the long awaited full support of PS1 games with sound, which bridged the gap with ePSP features on older firmware such as 3.18.
A few hours after the release, TheFlow has fixed a few annoying bugs (doubletap bug + Adrenaline menu after enabling/disabling WiFi), but, more importantly, he made Adrenaline open source. He also released version 3.1 today, while announcing he was taking a break from the scene.
You can download Adrenaline from the developerís github here. Please note that you will need a PS Vita running firmware 3.60 in order to run HENKaku and Adrenaline.