not the same thing. it plays differently, still full of bugs and there is no support for the old scripting language. all of the polished and great object files are incompatible with open clonk!
EDIT: Also I believe the recommended system specs for open clonk are a whole lot higher, but I am not entirely sure.
Clonk rage has pretty high demands as well, but I think a lot could be optimized by using 16bit depth only and reducing the amount of opengl deco effects (fire particles and stuff like that), which used to be configurable anyway. also the pandora has a low screen res compared to a pc.
clonk endeavor has similar gameplay, is free and has the source available. it's prettier than clonk planet but the user content is probably not as easily available as it is with clonk rage.
anyway, this game is a true gem. with the new control scheme it's also not as hard to learn anymore and if you are a fan of terraria, minecraft, liero, spelunker or the likes then you must play it! and it is free now so grab it! seriously, this game influenced me more than most! I played it when I was 16, and now 13 years later, occasionally I still like to play it.
EDIT2:
http://www.gp32x.de/board/index.php?/topic/55175-clonk-rage/
seems like pickle already ported the engine to pandora in 2010, but the game wasn't freeware back then. Please someone contact him and try this! I even still have my registration key for the game ^^. but now we wouldn't even need that!