Not a lawyer, don't even like lawyers. That said, I've done a bit of research on this (as applies here in the land of lawyers, the good ole' US of A). Basically, recording and performance fall under different licensing rules. If someone wants to record a cover of a song they need permission from the copyright holder of the song (i.e. lyrics and melody). This can be the individual songwriter but usually ends up being some faceless corporation. The agreement covers specifically what is to be recorded, how the recording is to be published or distributed, and so on. These are quite difficult to come by without either outright cash or an agreement for royalty sharing - this is why Ken would have had difficulty getting publishers to give him a license - he's not expecting revenue and it's pretty hard to convince a publishing company that twenty percent of nothing is a good deal. Neither publishing companies nor most songwriters are long-sighted enough to realize that if somebody like Ken is publishing covers and tutorials of their material thats going to translate eventually into increased revenues from performance licensing as armies of ukulele players take stage throughout the land.
Public performance of copyrighted songs rarely involves negotiation by the individual artist. Instead, venues are supposed to cover this issue by arrangements with ASCAP or BMI. Those arrangements fall into the nature of "on average we do X number of shows of Y number of songs for Z number of patrons." ASCAP and BMI periodically survey their member venues asking for detailed information about what songs are being played, and then distribute the money from dues-paying venues based on that sample data. The reason I know this is because this applies even to churches, though most Christian artists and publishers go through a different agency. Last year we got one of those survey requests where we had to report what songs had been performed in services during the previous month, what the average attendance was, etc.
I'm not sure what liability an individual artist might have if they played a venue that hadn't been paying their ASCAP or BMI dues. I suspect if the artist could reasonably show that they had a good faith expectation that the venue would be doing so (i.e. by playing at a venue that regularly presents musical programs) ASCAP or BMI would probably go after the venue and leave the artist alone.
In some cases the laws even protect the little guy, much as I hate to admit it. When a publishing company "publishes" music - allowing others to cover it via performance licensing, they don't really get to say, "everybody can cover the song except for this guy." There is a very good Beatles tribute band in our area. They are so good and so well known here that when Sir Paul was on tour a couple of years ago he tried to shut them down. Their lawyers told his people to take a hike, and made it stick. They were covered under the performance licensing of the venues where they played, not a recording license for specific material. I'm sure his people knew this, but figured they could throw their weight around and the local yocals would run for cover, at least while Paul was in town (I suspect that Paul realized that the guy who plays and sings his parts has a voice and skills at least the equal of what Paul had decades ago and he wasn't relishing any fresh comparisons with his "today" voice). Anyway, the singing knight didn't get his way, dear Paul ain't used to dealing with Texans, I guess.
The biggest problem is that nobody has figured out what kind of licensing should apply to online performances. Technically, it's a recording but you're never going to get a license for a YouTube recording. It's more like a performance, but it's a performance that goes on and on and may be for millions of people, yet there isn't significant revenue from it.
I think eventually ASCAP and BMI are going to have to come to some kind of "performance" licensing agreement with online "venues" like YouTube where they share revenues based on sample hit data. Both sides are going to have to give. ASCAP and BMI and the publishers they represent are going to have to acknowledge that the revenue stream from independent internet covers is very small when measured against the audience size and YouTube et. al. are going to have to recognize that member "indy" videos put them where they are - if they just blanket eliminate those videos they aren't going to have the kind of content that attracts as large an audience as they currently have.