if this helps anyone, a system wide deployment can be accomplished via 

/Aspera\\ Connect\\ Installer.app/Contents/Resources/install true

well, I tried to put the install app in /var/tmp, and then run /private/var/tmp/<path to the install script in the app> and it works from a shell script but not from a post install script from composer. Even tried 1>/dev/null thinking that their output is causing the error.

Then I noticed the AsperaApps.zip inside their app installer. Unzipped that, and what do you know. Now to deploy those apps with Composer.

Why do developers make their apps so hard for us to deploy... sigh.

So, in side the installer app they give us now (ARGH!) there's an install script. If you run...

...it will install system-wide.

They changed it yet again, now I use the following:

I lay the .pkg downloaded into /private/tmp/ then have a script that runs 

sudo installer -pkg /private/tmp/ASPERA4.2.2.135/ibm-aspera-connect_4.2.2.135_macOS_x86_64.pkg -target LocalSystem