  An important theorem of Ling states that if $G$ is any factorizable
non-fixing group of homeomorphisms of a paracompact space then its commutator
subgroup $[G,G]$ is perfect. This paper is devoted to further studies on the
algebraic structure (e.g. uniform perfectness, uniform simplicity) of $[G,G]$
and $[\tilde G,\tilde G]$, where $\tilde G$ is the universal covering group of
$G$. In particular, we prove that if $G$ is bounded factorizable non-fixing
group of homeomorphisms then $[G,G]$ is uniformly perfect (Corollary 3.4). The
case of open manifolds is also investigated. Examples of homeomorphism groups
illustrating the results are given.
