[Edit: Just for the heck of it, I went back and read the credits and introductions to both modules. Nowhere is there an explicit mention of Lewis Carrol. There are some vague allusions to the 'land where Alice went' and such, but that is about as close as you get to the author acknowledging the actual source material.]
EX1, pg. 27: "It is presented in a light-hearted and zany spirit. In order to get in all the necessary details, however, not too much space can be devoted to really capturing the true spirit of Dungeonland. Therefore, the Gentle Reader is urged to read Lewis Carroll's story,
Alice in Wonderland. Read this book carefully. You might even find you enjoy sections sufficiently to reread them. Do this just before you begin having your players adventure in Dungeonland, and then really let yourself go!"
EX2, pg. 26: "In order to be in the proper frame of mind for superior DMing of this module, I urge you to accept it as a fun experience first and foremost. Then, please pick up a copy of Lewis Carroll's
Through the Looking Glass. After you have finished reading this book (and that won't take long at all), you might find it helpful to re-read it. Then, with the intentions that the good Mr. Carroll had in mind when he penned this tale, undertake a masterful moderation of the scenario."
Again: I'm not defending the modules. I think they're poorly designed. But they are
explicitly adaptations of Carroll's work.
Actually it is true. There is a point in DL11 I believe (when the party is near the new Silvanesti in exile homeland) that it clearly says that new characters can be brought in if the main characters die and then even gives suggestions on new character ideas.
The implication is quite clear that the main characters are not to die up to this point.
DL2, pg. 3: "Since these NPCs appear in later DRAGONLANCE modules, try to make them have 'obscure deaths' if they are killed: If at all possible, their bodies should not be found. Then, when the NPCs appear in later modules, you have a chance to explain their presence. (...)
The same rule applies to the PCs on pages 17-18. Most of them have roles in future modules, and must be able to return to life somehow. This does not apply to PCs other than those who are part of the story." (emphasis added)
That's pretty explicit.
DL3, pg. 2: "Because DRAGONLANCE is a story, both heroes and villains often figure prominently in later modules. If “name” characters or villains should be killed, arrange “obscure deaths” for them. Their bodies should not be found. (...) When a “name” character no longer plays a part in the story, his death can occur. Player characters brought into this adventure from outside can be killed normally."
This is less explicit, but the implication is pretty clear that PCs who
aren't brought in from the outside aren't to be killed. This text was repeated in DL4. In DL5 the section was expanded with a more explicit discussion of the comic book origins of the "obscure death" concept, and then--
DL5, pg. 5: "If the character is a PC, you can handle it the same way as an NPC (but tell the PC how he "miraculously survived" so that he can tell the others when he shows up), or you can create a short one-on-one adventure so that the PC can role-play his way out of danger."
This is followed by a list of ideas including comas, miraculous escapes, and being saved by an NPC.
The rule is not stated in DL6, although there are references to the DM applying the rule to the NPC Sleet. In DL7 the rule is again stated for NPCs, but PCs are not mentioned.
And then the ban on PC death was lifted in DL8.
DL8, pg. 2: "Beginning with this module, no PC is subject to the obscure death rule. If a PC dies in this or later adventures -- say goodbye!"
When the series was reprinted in the Dragonlance Classics trilogy, it looks like they tried to eliminate the PC application of the rule. (Which may be why some people think it never existed.) But it still creeps in by implication.
DLC2, Chapter 10, pg. 52: "Beginning with this chapter, no PC is subject to the obscure death scenario. If a PC dies in this or later adventures--say goodbye!"
DLC2, Chapter 13, pg. 73: "Remember that player characters are no longer subject to obscure deaths. If a PC dies, he's gone forever!"