First off, this would only work, if the right conditions are met.
First off, how Normal DCC works.
When a Client requests a DCC session, it sends the request, with the IP and port that the client should connect to.
The eggdrop will check this information, to make sure it knows you. If so, the it makes the connection to the IP and port given by the client.
This requires two things.
1: The IP that has been sent by the client is correct
2: That the client can accept the connection on this IP and port.
Number 1 is normaly true (if using mIRC, make sure). Number 2 is affected by NAT.
If the Client is behind a NAT router (be it a physical router or second box with 2 NICs), then the IP sent must be that of the NAT router and a port that has been set to forward to the machine you are using the client on.
If this is all true, then DCC should work fine.
How reverse DCC works
There are two type of reverse DCC.
1: To initiate a normal DCC session, but send a PORT number of 0. The other end should then send a IP and port to connect on. Eggdrop doesn't support this (I don't think mIRC does either). Eggdrop is due to support this in the next major release (1.8 series, not 1.6).
2: With eggdrop, you send a command that causes to send a DCC connection request to you (this si the one you talk of).
This works by switching all the above around. IE, the bot will send the IP and port, not the client, and the client will make the connection attempt.
As such, for the above ot work, you revser points 1 and 2 above.
1: The bot must send the right IP
2: The bot must be able to answer on the IP and port sent.
If it comes to the point where bot sides of the connection (both the bot and the client side) have NAT connections, there is no other way to get around this, than by using port forwarding in the NAT router.
For this, see the many guides to setting up mIRC fir use behind a NAT router (the same can be applied to eggdrop, only you have to change the settings in the config file, they are named differently and you should use the nat-ip setting).
I've been lurking around, trying to find some more info on this script, and it appears that it converts the IPs to LONG and uses that as connection data. Does this sound appropriate?