Re: Broken, yes... and not fixable.
> - MSDOS - bought from Tim Paterson (who copied the design of CP/M)
There are some that say that Tim copied the code of CP/M, specifically of version 1.2.
Both SCP and MS were OEM licenced for CP/M. SCP for their Zebra range, MS for the Z80 Softcard for the Apple II. Both had all the source code that DRI would supply to its OEMs. The BDOS, however, was written in PL/M and supplied as a binary because it was invarient. At the time there were 'commented decompilers' available for various software, including CP/M BDOS. There was also an Intel 8080 -> 8086 ASM translator.
SCP was developing 8086 processor boards for their Zebra machines and needed an OS to test with. It has been claimed that they decompiled the BDOS, ran it through the Intel translator and recompiled (with many fixups) to get the initial QDOS. This would have had CP/M file system which would have been needed as they would have built the system the system using CP/M, swapped the processor board and rebooted.
The MS FAT filesystem was added later from MS's 'Stand-alone BASIC'.
It is alleged that when IBM was testing PC-DOS, Gary Kildal was able to enter a particular command and get a DRI copyright message displayed. IBM settled giving Gary money, agreeing to sell CP/M-86 alongside PC-DOS and rewriting the BDOS - which became version 1.25.
The reason that it is alleged to be version 1.2 that was copied is that it had a specific bug in handling the FCBs and this bug existed in the earliest MS-DOS and PC-DOS - prior to 1.25.
SCP initially licenced Microsoft non-exclusively for 86-DOS (or SCP-DOS) running on 8086 CPUs. In theory its use on 8088 was breaking the licence. Later, MS purchased it outright and this gave SCP as many free copies of MS-DOS as required as long as they were sold with a computer. When the SCP factory burned down they started selling a V20 chip (faster 8088 clone with 8080 support) with a copy of MS-DOS. MS had to buy back the agreement for a million or so.
> - Internet Explorer - licensed from Spyglass
Spyglass wrote IE, it was not a version of Mosaic but was new code, on the basis of getting a royalty ($5?) for every copy sold. MS gave away IE and thus none were sold and no royalties were paid. Spyglass sued and eventually won a settlement of some millions, but by then the company had folded.