A few replies:
Turjan said:
This is an interesting question. Has WotC PI'd the word "Druid"? Can I make a d20 class and call it "Druid"? I know that it would not be very convenient to make a class that has the same name as the WotC class, but I suppose it's pefectly valid.
As was noted above, using the word "druid" is kind of moot because it is part of the SRD, so if you're releasing a OGL product your s.15 will already contain the SRD copyright which covers the word "druid" in the context of the game. Also, as was pointed out, there have been alternate classes with the same name as a core SRD one, like the case of Slaine's druid, or even Monte Cook's alternate ranger. And no, you cannot PI the word "druid" (or bard, ranger, wizard, cleric, etc. for that matter) because it would be like me PI-ing the word "the," as was pointed above. You CAN PI words like "warmain" and "unfettered" (Arcana Unearthed), though not "witch" (also from Arcana Unearthed). Notice that this is why WotC decided to pick very specific things to PI when they released the last version of the d20 System Guide, things like "beholder," "displacer beast," "illithid," or specifc phrases containing the names of the planes like "Bleak Eternity of Gehenna," or "Peaceable Kingdoms of Arcadia;" you can still use the words Gehenna and Arcadia, but as nouns without the extra adjectives WotC put on them.
Turjan said:
As far as "Akashic" goes, the whole internet is full of this word. There are domains with this name. There is a company called "Akashic Books". There is a band called "Akashic". I can only guess that trying to force a PI in this case should be considered futile, but then again, I'm no lawyer, and laws have often managed to surprise me so far

. Any insight into this would be welcome

.
Like I said, the word "Akashic" is part of the common parlance, so you can't just PI it indiscriminately. I don't know why Malhavoc went ahead and PI-ed it, other than they PI every name of anything in their books (spells, feats, places, people, classes, etc.--the infamous "crippled OGC" that one hears about sometimes, but that's another can of worms). I can understand a PI on the word "Akashic" in relation to a character class which taps into the collective unconscious that seems to describe what the "Akashic Records" are in order to gain access to knowledge stored in this vast library of experiences. And even that I would, personally, be iffy with because once you read what the Akashic Records are supposed to be it's almost a no-brainer coming up with the concept of a class (either core or prestige) that does exactly what I described. I do think, however, that you couldn't just go and call that class just "Akashic" without having to be very careful about infringing the OGL.
Turjan said:
I'm just not sure whether it's principally possible to PI mundane terms like "druid". "Akashic" is a bit more exotic, but nevertheless widely used in the New Age community. I didn't look whether the record company or the book company held any trademarks, though.
No, you just can't go and claim as your Product Identity mundane terms just like that; the way I see it, if I can find it in the Unabridged Oxford English Dictionary (or the equivalent in another language as well, like the Dictionary of the Royal Spanish Academy, for example) it is fair game and un-PI-able. Trademarks are different, though, becaue you can trademark a mundane term, but it has to be in a specifc context. The words "have," "it," "your," and "way" cannot be trademarked by themselves, but "Have it your way" as a phrase in the context of a Burger King ad can be (and is) trademarked. So the record company and the book company may indeed have trademarks on the word "Akashic" but it's going to be in relation to the band or the publishing company, and most likely it will be alongside a specific logotype of the word. PI and trademarks are not the same thing, though they behave similarly in a few cases.
Again, IANAL. I would love a lawyer to drop by and help sort this out.