No they are not. Widgetlocker is waaay better than Go Locker.
They are the same in the sense that they replace your lockscreen, allowing you change its looks and increase in functionality. The difference being, Go Locker uses preset themes you can choose from, and the ability to change shortcuts, and that's about it. You can only use what is given you. If the theme only has 2 shortcut spots available, that's it. And you cant change the way the music controller looks.
Widgetlocker on the other hand acts like an extra homescreen. You can put any widget on it just like a homescreen, and the sliders have different themes as well. I actually for one use completely invisible sliders containing shortcuts to unlock, camera, inbox and dialer. Basically, it offers more freedom to design it the way you want to.
