formulae <- list(lambda1 ~ lambda0, mu1 ~ mu0, q10 ~ q01)
constrain(lik, formulae=formulae)

f1 <- "lambda1 ~ lambda0"
f2 <- "mu1 ~ mu0"
f3 <- "q10 ~ q01"

formulae <- as.formula(paste(f1,f2,f3, collapse=","))