Perhaps they came out with this development kit at the same time they stopped giving out HyperCard with the Macs and switched to the Player? The "development kit" name may have referred to the fact that you could actually program with this version as opposed to the player which only let you, well, play stacks.
I have HC 2.0 on an Apple-branded disk, it came with my Mac LC. There was a little skinny manual (Apple-branded) that came with it as well. You only got three stacks though--Addresses with Audio, Appointments with Audio, and Audio Help. I think they bundled that with the LC and IIsi to emphasize the new microphone features. The home stack was completely different from any other HC home I've seen. The manual didn't tell you how to program, just how to use the stacks. The HC on the disk was a full version but you had to type a script in to access the programming features, I think David Pogue and Joseph Schorr's "Macworld Mac & Power Mac Secrets" said what to type. (Apple probably wanted novices to not program so they didn't mess up those stacks because like I said, I think they were pushing the microphone features with the LC and IIsi around that time, then after realizing that people went in to activate it they went to the player--which was probably also to make more money by trying to sell the actual HyperCard program).
A version of 2.1 came bundled with Spelunx, actually. I think it has a 2.x home stack on the disk but nothing else. Remember that Spelunx is HyperCard based. The disk is a Broderbund disk, though, not an Apple or a Claris. They threw this in for people still running 1.x on their Macs who needed to upgrade, I think the installation instruction sheet (which I have so I can verify this) says about this.
I think 2.1 was still bundled with some of the Macs when they launched the Claris product. I may be wrong on this but I think full versions of 2.1 were often bundled with Macs, maybe as bundles. The one that schools used to get with the Educator HomeCard program was 2.0 or 2.1 if I recall.
I know HC 1.x was, I've got an SE that had them among the original disks.
I have HC 2.0 on an Apple-branded disk, it came with my Mac LC. There was a little skinny manual (Apple-branded) that came with it as well. You only got three stacks though--Addresses with Audio, Appointments with Audio, and Audio Help. I think they bundled that with the LC and IIsi to emphasize the new microphone features. The home stack was completely different from any other HC home I've seen. The manual didn't tell you how to program, just how to use the stacks. The HC on the disk was a full version but you had to type a script in to access the programming features, I think David Pogue and Joseph Schorr's "Macworld Mac & Power Mac Secrets" said what to type. (Apple probably wanted novices to not program so they didn't mess up those stacks because like I said, I think they were pushing the microphone features with the LC and IIsi around that time, then after realizing that people went in to activate it they went to the player--which was probably also to make more money by trying to sell the actual HyperCard program).
A version of 2.1 came bundled with Spelunx, actually. I think it has a 2.x home stack on the disk but nothing else. Remember that Spelunx is HyperCard based. The disk is a Broderbund disk, though, not an Apple or a Claris. They threw this in for people still running 1.x on their Macs who needed to upgrade, I think the installation instruction sheet (which I have so I can verify this) says about this.
I think 2.1 was still bundled with some of the Macs when they launched the Claris product. I may be wrong on this but I think full versions of 2.1 were often bundled with Macs, maybe as bundles. The one that schools used to get with the Educator HomeCard program was 2.0 or 2.1 if I recall.
I know HC 1.x was, I've got an SE that had them among the original disks.