leshan.jar is not open source ?

[jinxinxin163]

Hi author：
I get source code from https://github.com/eclipse/leshan and build a lenshan.jar
and then build lwm2m_over_mqtt using my leshan.jar
but i encounter many undefine errors
cannot find symbol [ERROR] symbol: class LwM2mRequestVisitor
cannot find symbol [ERROR] symbol: class LinkObject
cannot find symbol [ERROR] symbol: class ObservationRegistry
and i can't find the defination of LinkObject and LwM2mRequestVisitor under leshan code base
why?could you help me ? Thanks