In this image you can see the "family tree" of StarCraft bots. Each black circle represents a new release of the bot. Not all bots are included in this, but UAlbertabot is the bot that has the most code of it inside other bots.
Of course, the further along the development, the less seems to remain of that code. In LetaBot there is more code remaining from the building placement from the Nov bot than code from UAlbertabot. However if you look at its architecture, you will still see the remains of the influences of UAlbertabot in there.
That seems to be the general trend. If a bot starts out based on another bot, it will eventually replace most of the code to suit the needs of the author, but the useful classes (which are kinda like BW AI libraries like the BWEM) remain, and so does the architecture. This can be seen when you look at the source code of AIUR and IceLab which is based on AIUR.
One other thing to note, is that Stone and Iron (both made by the same author, the only bots in the family tree for which this is the case) managed to get 1st place AIIDE 2016, 2nd place CIG 2016, and 3rd place twice in a row on the SSCAI without having the bot based on any other bot.
So, the success of a bot mainly comes down to the skill/knowledge of the programmer. Using the code of other bots can help you get started, but the main factor for success still remains the ability to add new techniques. Simply taking the best technique(s) of each open source bot and putting them together in one giant bot won't get you 1st place at a StarCraft AI tournament.
Also, there might be a new bot based off SteamHammer as well. So keep on the lookout for that: