PS4 Playground 1.76, 3.55 Port, PS4 Playground 1.01, 1.05 Port, 3.x Playground and even a PS3 Port of CTurt's original PS4 WebKit Playground today @zecoxao ported it to PlayStation 4 Firmware 1.50b with details below from his Twitter feed.
There are also more PS4 MEME's courtesy of @Ginsor, @X41 and @xxmcvapourxx added to the PSXHAX Shoutbox MOTD for any developers interested!
Download: playground-1.50b-master.zip / GIT / PS4-Custom-WebKit-Playground_v2.00.01.rar (2.0 MB) / Zecoxao's Github (even more recent updates)
According to the updated README.md this PS4 playground branch is currently for firmwares 1.76 / 1.50b / 1.01 only at the moment, and for those unaware it's a collection of PS4 tools and experiments using the WebKit exploit.
Thanks to @romantizma for the heads-up earlier this morning in the PSXHAX Shoutbox!