Runesword is a PC game, don't know if there is a Mac version too. I have tested the scenario with Runesword 1 and it worked well, can't say much about the compatibility with the RuneSword 2 engine. Occasionally the game crashes, especially if a monster uses a gaze attack, so save frequently. Both the engine and the scenario are freeware, the author of the engine recommends a donation for charity, however. The version of Forging Britannia which is available for download on the official site may have some bugs like invisible NPCs, ladders leading to nowhere etc. although the author is always working on updates. If you have troubles running the game, ask me for a hacked but playable version.