The Celestial Empire No Longer Available
On the other hand, Chaosium can still sell the Alephtar Games books and PDFs. However, it seems they have disappeared from Chaosium's catalogue on their web shop.
Bottom line: if you're interested in TCE and see the book in a shop or on a web-site, do purchase it! It will become impossible once the current stock has been sold out.
Also, given the amount of work that it would involve, I have currently no plans whatsoever to re-write the book to make it compatible with another set of D100-based rules. I'm also way too busy with writing and playtesting Oriental Monsters & Magic.