At what point is it no longer d20?

[Voneth]

According to Guardians of Order, as long as you use a d20 and add modifers to be a DC, you've got a "d20 system" and they have had no problems with being complient.

Green Ronin, however, played it safe and made their product OGL (it was also because a lot of people complained about the compatability of GoO's products (Silver Age Sentinels) with other d20 books.)

M&M actually did some changes just as radical as yours:
*removed hit points and created a new "Damage Savings Throw" system
*Character level became "power levels" Which meant a player got so many character points per level to create a character and the level also cap out the maximum amount of skills, power, etc.
* optional rules to convert BAB and Defense into ... skills! Sound familiar
*assign point values to attributes, skills, feats and even powers.

It goes on, but you get the idea. Despite these changes, I think most people still precieve M&M to be a "d20" game.

 

[Ranger REG]

Okay, so at what point did I completely leave the d20 system? Or am I still in it? I've shifted the physical scores, combat is bound to be a lot more dangerous, and there are no more levels. But I'm still using d20+ranks to determine whether or not I succeed at things. That mechanic is utterly unchanged.

More a philosophical point than anything else. I'm wondering how long it remains "My grandfather's axe" -- how many times you can replace the head and the haft before it's a new animal... or, you know, something like that.

You mean how many times you can change a grandfather's axe before it becomes a blender?

As one poster indicated, the rules system is based on the most fundamental mechanic: d20 + modifier vs. DC

Of course, that could also describe Palladium's Megaversal System, a d20-based ruleset.

I guess it is the recognition of certain core elements as well as the fundamental mechanic by gamers to distinguish d20 from other known systems. For example, the ability names (e.g., Str, Int) & scores, the saving throws (e.g., Fort, Ref), skill system, hit point system, etc. Of course, one or two elements can be removed or replaced with different mechanics but usually not all of them.

I guess you have to decide how far you wish to deviate from the standard ruleset outlined in the SRD. Sometimes it is best to make the rules fit the game, rather than make the game fit the rules.